1892.] MICROSCOPICAL JOURNAL. 155 



Closterium angustatum, var. clavatum, var. nov. Hast. 

 (Plate I, tig. 7, X 2SO.) Cells sub-lineai", 12-36 times as long as 

 wide, ends clavate, apices rounded ; four prominent costiu ; vac- 

 uole terminal with dancing granules. Diameter 35-30 m., ends 

 two-thirds as wide. Ponds and streams, Rochester, N. H. Oct. 

 20, 'SS. 



EXPLANATION OF THE PLATE. 



Fig. kj. Eu.-istrum magnificum variety 

 crassioides, var. nov. WoUe, .\ 

 500. 

 FjG. 1(5. Same, side view, .\ 500. 

 Fig. ic. Same, end view, x 500. 

 Fig. 2rt. Xanthidium tnincatum, spec. 



Fig. 3. Staurastnim megaloiio'.iim, Nord. 



var. Obtusiim, var. nov. Wolle. 



Front view, x 500. 

 Fig. 4. Closterium robustum, spec. nov. 



Hastings, x 250. 

 P"iG. 5. Closterium maculatum, spec. nov. 



nov. Hastings. Front view, x 500. I Hastings, x 500. 



Fig. lb. Same, side view, x 500. i Fig. 6. Closterium lineatiim, variety costa- 



FiG. 2C. Same, end view, x 500. I tum, var. nov. Wolle, x 250. 



Fig. 7. Closterim angustatum Kg. variety 

 I clavatum var. nov. Hastings. 



Microscopical Illustrations. 



By henry L. TOLMAN, 



CHICAGO, ILL. 



One of the most difficult features in connection with the illus- 

 tration of scientific articles is the reproduction of the photo-micro- 

 graphs or camera-lucida drawings. If the object contains a large 

 amount of detail, a photograph will be the only way by which all 

 the minutiaican be preserved, but no wood-cut can entirely repro- 

 duce the original. Of course, it is not always necessary that 

 everything which is seen under the microscope should be seen in 

 the book illustration, and Just here is the point where authorities 

 differ on the requisites of a good wood-cut or engraving. Some 

 hold that only the salient parts of an object need be represented ; 

 in fact, that the picture is better for having omitted from it all but 

 the few leading features, to which the writer desires to call atten- 

 tion. Others claim that the picture should represent just what 

 the eye sees under the microscope, free from any of the possible 

 or intentional errors of the artist. There is, undoubtedly, much 

 to be said on both sides of the question. 



Those who have studied the astonishing cuts called " dia- 

 grammatic representations," the counterpart of which they vainly 

 search for in nature, will be strongly in favor of any method 

 which reproduces an object so it can be recognized, and the ten- 

 dency of the art of the present day seems to be in this direction. 

 Fortunately with this demand comes an improvement in the 

 manner of reproducing photographs and drawings of every kind, 

 which deseives a somewhat extended notice. This is by what 

 is known as the half-tone process, . which consists of a photo- 

 graphic copy of the original on a zinc or copper plate and then 

 etching the plate until the drawing appears in relief, and is 

 printed from like an electrotype.' In order to convert the smooth. 



